Method and a Device for the Dewatering of a Fibre Suspension Supplied by a Nozzle Assembly

ABSTRACT

A vertically elongate and oriented container ( 1 ) of wire cloth material contains a vertically oriented nozzle assembly ( 2 ), which sprays a fiber suspension against the inner wall of the container. The nozzle assembly is revolved around the axis of the container and is displaced backwards and forwards vertically so that the suspension sprays, which in the direction radially outward widen against the shell wall of the container ( 1 ) afford a cleaning effect in respect of deposited fibers on the inner wall of the container ( 1 ) at the same time as the liquid of the suspension efficiently is separated through the container wall in order to then be collected in a housing ( 9 ) surrounding the container ( 1 ).

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a U.S. national stage application of International App. No. PCT/SE2008/000510, filed Sep. 12, 2008, the disclosure of which is incorporated by reference herein, and claims priority on Swedish Application No. 0702091-0, filed Sep. 17, 2007, the disclosure of which is incorporated by reference herein.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The invention relates to a method and a device for the dewatering of a fiber suspension.

A fiber suspension may, for instance, be the liquid suspension removed from a stock, which contains a residual amount of fibers. It may be desirable to, from the suspension, separate at least a part of the particles/fibers, in order to be able to use the same in a useful way. Furthermore, it is necessary or favorable to, from the suspension, remove as great a part of the particles/fibers as possible before the liquid part thereof (water) is brought back to the environment.

It is in that connection previously well known that it is possible to lead the suspension through a screening material through which the liquid share of the suspension passes, the fiber fraction largely being collected on the screening material and then being collected for further handling.

A problem is to carry out such a separation in an efficient way. Therefore, an object of the invention is to provide a technique by which separation of fibers from a fiber suspension can be carried out in a simple and efficient manner.

SUMMARY OF THE INVENTION

The invention comprises essentially that the screening material is formed to a vertically orientated elongate container, that the suspension is introduced into the container via a vertical elongate nozzle assembly, which in all essentials is concentrically arranged in the container, and that the nozzle assembly is arranged to spray the suspension via a plurality of nozzles spaced-apart around the assembly against the inside of the shell wall of the container.

The nozzle assembly is displaced in relation to the container in the axial direction thereof. The nozzle assembly, which preferably carries two or more groups of nozzles spaced-apart along the assembly, which are distributed around the circumference of the assembly, can furthermore be rotated in relation to the substantially vertical axis of the container.

Since the container is stationary, the bottom part of the container may be provided with a valve device or lock device, through which a fiber fraction accumulated in the bottom part of the container can be withdrawn. A liquid level sensor is arranged to detect the liquid level in the container and is arranged to control the flow of suspension supplied to the container in such a manner that the liquid level of the container lies under the nozzle assembly. The container may be received in a surrounding housing, which catches liquid separated from the suspension and leads the same away.

The invention will in the following be described in the form of example, reference being made to the appended drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view which shows an axial sectioned through the device according to the invention.

FIG. 2 is a schematic view which shows a section taken along line II-II in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, an elongate vertically orientated tubular container 1 of wire cloth material is schematically shown, which in the upper end thereof is carried by a structure not closer shown. In the upper part of the container 1, a nozzle assembly 2 is shown comprising a generally vertically directed pipe 3, which connects to a plurality of groups 4 of nozzles 5, the nozzles 5 being arranged to spray suspension introduced via the pipe 3 radially outward toward the inside of the container 1. From FIG. 2 it can be seen that the nozzles of the respective group 4 are distributed around the circumference of the assembly 2. The assembly 2 is in all essentials concentric with the container 1 and is arranged manageable around the axis thereof and of the container 1 by means of a schematically shown driving engine 7.

A suspension is supplied to the pipe 3 by elevated pressure, for instance via a swivel connection 8. At the lower end part of the container 1, at a distance under the nozzle assembly 2, there is a valve device 10. The lower end of the container connects to a pipe 11 having a valve device 10. The valve device 10 may, for instance, consist of two slide valves 15 spaced-apart along the pipe 11, which can be arranged to form a lock in the pipe 11 leaning downward from the container. The valve device 10 is driven in order to enable feeding out of a fiber suspension of elevated fiber content, from the lower part of the container 1 or the upper part of the pipe 11. This fraction may, for instance, under the impact of gravity be fed out via the valve device of the pipe 11 to a collecting container 14 and may from there be fed out onto a conveyor belt 12, which, for instance, may consist of wire cloth or the like in order to mechanically be dewatered in contact with a clamping device 13 lying above, for instance, in the form of an endless press band of screen cloth, which via, for instance, squeezing rollers is pressed against the fiber material on the conveyor belt 12.

The container 1 is surrounded by a housing 9, the walls of which are lying at a radial distance outside the container 1 and has a bottom outlet 91. Suspension liquid leaving through the wall of the container 1 is collected in the housing 9 and is led away via the drainage 91 thereof.

The engine 7 is advantageously arranged to impart the nozzle assembly 2, in addition to a rotary motion, an axial reciprocating motion, so that the suspension spray which is leaving the respective nozzle 5 also can carry out a scraping function in respect of fibers tending to deposit on the inside of the container 1, so that deposited fibers move downward toward the bottom of the container. The suspension flow to the container is adapted so that the container in all essentials is not flowed by the suspension, i.e., so that the suspension jets freely pass between nozzle and container wall. The jets are given such high speed that a substantial share of the liquid of the suspension leaves through the wire cloth, while the fibers to a substantial share are retained in the container. 

1-10. (canceled)
 11. A method for the dewatering of a fiber suspension, comprising the steps of: introducing from above a fiber suspension under pressure through a nozzle assembly into an elongate tubular vertically orientated container made of a fiber separation material; wherein the elongate tubular vertically orientated container defines a vertically orientated axis; wherein the nozzle assembly has a plurality of nozzles spaced-apart around the axis of the container and wherein the nozzle assembly is placed centrally in the elongate tubular vertically orientated container; and displacing the nozzle assembly in an axial direction along the axis of elongate tubular vertically orientated container.
 12. The method of claim 11 wherein the nozzle assembly is displaced backwards and forwards along the axial direction of the elongate tubular vertically orientated container.
 13. The method of claim 11 wherein the container is kept stationary.
 14. The method of claim 11 wherein the nozzle assembly is imparted a rotary motion in relation to the container about the axis of the container.
 15. The method of claim 12 wherein the nozzle assembly is imparted a rotary motion in relation to the container about the axis of the container.
 16. The method of claim 13 wherein the nozzle assembly is imparted a rotary motion in relation to the container about the axis of the container.
 17. The method of claim 11, wherein the fiber suspension is sprayed through a plurality of groups of nozzles which groups of nozzles are spaced-apart in the axial direction along the nozzle assembly.
 18. The method of claim 11, wherein the fiber separation material is a wire cloth.
 19. A device for the dewatering of a fiber suspension, comprising: an elongate and vertically orientated tubular container of a liquid-permeable fiber-separating material which defines a vertical axis and an inner circumference wall; a nozzle assembly connected to a source of pressurized fiber suspension, and placed centrally in the elongate and vertically orientated tubular container; and wherein the nozzle assembly has a plurality of nozzles, which are arranged to direct sprays of a fiber suspension against the inside of the circumference wall of the elongate and vertically orientated tubular container.
 20. The device of claim 19, wherein the liquid-permeable fiber-separating material is a wire cloth.
 21. The device of claim 19, wherein the nozzle assembly has a plurality of groups of nozzles spaced-apart along the nozzle assembly, the nozzles of the groups being spaced-apart being circumferentially spaced on the nozzle assembly.
 22. The device of claim 19, wherein the nozzle assembly is mounted for rotation to a driving assembly so as to be driven in rotation about the vertical axis of the container.
 23. The device of claim 20, wherein the nozzle assembly is mounted for rotation to a driving assembly so as to be driven in rotation about the axis of the container.
 24. The device of claim 20, wherein the nozzle assembly is mounted to the driving assembly for reciprocal motion along the axis of the elongate and vertically orientated tubular container, and wherein said vertically orientated tubular container is stationarily mounted; a housing spaced from and enclosing the vertically oriented tubular container and arranged to collect suspension liquid from the source of pressurized fiber suspension; and wherein the housing has portions forming a bottom drainage arranged to lead away suspension liquid from the housing.
 25. The device of claim 23, wherein the nozzle assembly is mounted to the driving assembly for reciprocal motion along the axis of the elongate and vertically orientated tubular container, and wherein said vertically orientated tubular container is stationarily mounted, and further comprising: a housing spaced from and enclosing the vertically oriented tubular container and arranged to collect suspension liquid from the source of pressurized fiber suspension; and wherein the housing has portions forming a bottom drainage arranged to lead away suspension liquid from the housing.
 26. The device of claim 19, further comprising a valve device connected to a lower end part of the elongate and vertically orientated tubular container and arranged to enable selectable leading out of a suspension fraction having elevated fiber content from the lower end part of the container.
 27. The device of claim 25, further comprising a valve device connected to a lower end part of the elongate and vertically orientated tubular container and arranged to enable selectable leading out of a suspension fraction having elevated fiber content from the lower end part of the container. 